Three ethical issues around pig heart transplants

A US man has become the world's first person to get a heart transplant from a genetically modified pig.

The case is of 57-year-old David Bennett, who doctors say was too ill to qualify for a human heart.
After the surgery, he is doing well now.
The surgery is being hailed by many as a medical breakthrough that could shorten transplant waiting times and change the lives of patients around the world.
But some are questioning if the procedure can be ethically justified.
They have pointed to potential moral trouble spots over patient safety, animal rights and religious concerns.

How was it done?

The heart used in the transplant came from a pig with several genetic modifications, including some to knock out genes that trigger the human immune system.
Since the human immune system rejects anything that is foreign, whether from another person who is immunologically matched to the recipient or from a different species such as a pig, scientists had to tweak the pig genome to make the organ less likely to be rejected.
Scientists altered 10 genes in the pig whose heart was used for Mr Bennett's transplant so it would not be rejected by his body.
The pig had its heart removed on the morning of the operation.

The science behind gene modification

The genome-editing tool CRISPR/Cas9 allows precise removal of specific genes.
A genetically modified pig cell is fused with a pig ovum that has its DNA removed.
The ova that contain only the genetically engineered genome start dividing to become pig foetuses.
This is the same technique that was used to clone Dolly, the sheep. The embryos are then implanted into surrogate mothers.
The gestation period is just 114 days, unlike in the case of humans.
Pigs have been preferred as ideal candidates for xenotransplantation despite their immune system being different from humans for the simple reason that the porcine organs are anatomically similar to those of humans.

What are the ethical issues involved in experimental surgery?

The medical implications

This is an experimental surgery, and brings with it huge risks for the patient.
Even well-matched human donor organs can be rejected after they are transplanted - and with animal organs the danger is likely to be higher.
Doctors have been trying to use animal organs for what is known as xenotransplantation for decades, with mixed success.
In 1984, doctors in California tried to save a baby girl's life by giving her the heart of a baboon, but she died 21 days later.
While such treatments are very, very risky, some medical ethicists say they should still go ahead if the patient knows the risks.

Why was Mr Bennett's case justified by the doctor?

Doctors who worked on Mr Bennett's case say the operation was justified because he had no other treatment options and would have died without it.
Mr Bennett's transplant was not performed as part of a clinical trial, as is usually required for experimental treatments.
And the drugs he was given have not yet been tested for use in non-human primates.

Animal rights

Mr Bennett's treatment has also re-sparked a debate over the use of pigs for human transplants, which many animal rights groups oppose.
- One of them, People for the Ethical Treatment of Animals (PETA) has condemned Mr Bennett's pig heart transplant as "unethical, dangerous, and a tremendous waste of resources".
"Animals aren't tool-sheds to be raided but complex, intelligent beings," PETA said.
It is wrong to modify the genes of animals to make them more like humans.
Animals have a right to live their lives, without being genetically manipulated with all the pain and trauma this entails, only to be killed and their organs harvested.
Some campaigners have concerns regarding the unknown long-term effects of genetic modification on the pig's health.

Religion

Another quandary could emerge around those whose faiths might mean it is tricky for them to receive an animal organ.
Pigs are chosen as the relevant organs are a similar size to humans' - and because pigs are relatively easy to breed and raise in captivity.
But how does this choice affect Jewish or Muslim patients, whose religions have strict rules on the animal?
Although Jewish law forbids Jews from raising or eating pigs, receiving a pig heart is "not in any way a violation of the Jewish dietary laws.”